The 559 area code is a vital telecommunications identifier for a large, agriculturally rich, and rapidly growing region of Central California. As of December 2025, this area code is at the center of a significant change: the introduction of a new overlay code. This article provides a deep dive into the 559 area code’s exact geographic location, the major cities and counties it covers, and the critical details you need to know about the new 357 area code overlay.

Originally created in 1998, the 559 code was split from the older 209 area code to accommodate the growing demand for new phone numbers in the San Joaquin Valley. The impending 357 overlay, announced by the California Public Utilities Commission (CPUC), marks the next major evolution for this region's telephone numbering plan, ensuring the area can continue to issue new numbers well into the future.

The Definitive Geographic Location of the 559 Area Code

The 559 area code is situated exclusively within the state of California, covering a vast swath of the central part of the state. It is primarily associated with the fertile and economically significant San Joaquin Valley.

Counties Served by the 559 Area Code

The 559 area code is not confined to a single county but spans all or portions of six distinct counties. This broad coverage is why the code is so crucial to the region's infrastructure.

• Fresno County: Home to the largest population center in the area.
• Tulare County: A major agricultural hub.
• Kings County: Located to the south of Fresno.
• Madera County: Just north of Fresno County.
• Mariposa County: Includes a portion of the western entrance to Yosemite National Park.
• Merced County: Only a small portion of this county is covered, with the majority belonging to the 209 area code.

Major Cities and Communities

The 559 area code is the primary identifier for numerous municipalities, from large metropolitan areas to smaller, historic communities. The following is a list of the most prominent cities within the 559 boundary:

• Fresno: The largest city and the economic center of the region.
• Visalia: The largest city in Tulare County.
• Clovis: A major suburb immediately east of Fresno.
• Madera: The county seat of Madera County.
• Reedley: Known as the "Fruit Basket of the World."
• Sanger: Located east of Fresno.
• Selma: Known as the "Raisin Capital of the World."
• Coalinga: Located in the western part of Fresno County.
• Parlier, Kerman, Kingsburg, Mendota: Other significant communities.

7 Critical Facts About the 559 Area Code and the New 357 Overlay

The most important and current information about the 559 area code revolves around the impending change that will affect how every resident and business in the region makes a phone call. The introduction of the 357 area code as an overlay is a direct response to the depletion of available 559 prefixes.

1. The New Code is an Overlay, Not a Split

Unlike the original split from the 209 area code, the new 357 code will be an overlay. This means the 357 area code will serve the exact same geographic region as the existing 559 area code. No one will be forced to change their current 559 number.

2. Mandatory 10-Digit Dialing is Required

The most significant change for all residents is the requirement for 10-digit dialing. Once the overlay is implemented, every call made—even local calls from one 559 number to another 559 number—must include the area code. This includes dialing "1" before the area code and the seven-digit number.

3. The New 357 Code Rollout Begins in 2025

The California Public Utilities Commission (CPUC) announced the new 357 area code will begin being issued to customers starting in 2025. This timeline is subject to minor adjustments but signals that the transition is imminent.

4. Existing 559 Numbers Will Not Change

Current customers with a 559 phone number will retain their existing number and will not be required to change it. The 357 code will only be assigned to new telephone lines or services once the available 559 numbers are exhausted.

5. Time Zone is Pacific Time (PT)

The entire 559 area code region operates in the Pacific Time Zone (PT), which observes Pacific Daylight Time (PDT) during the summer months. This is consistent across all the counties it serves.

6. The 559 Code’s Creation Date

The 559 area code was first put into service on November 14, 1998. It was a result of a geographic split from the 209 area code, which previously covered the entire Central Valley region.

7. Essential Steps to Prepare for the Overlay

To ensure a smooth transition, residents and businesses should take proactive steps. These include:

• Reprogramming or updating any automatic dialing equipment, such as life safety systems, PBXs, fax machines, internet dial-up numbers, and security systems, to include the 10-digit format.
• Ensuring all advertising and business materials (letterhead, business cards, websites) include the area code.
• Educating family members, employees, and customers about the new 10-digit dialing requirement.

The Economic Importance of the 559 Region

The 559 area code covers a region that is a powerhouse for California's economy, particularly in agriculture. The San Joaquin Valley is one of the most productive agricultural regions in the world, often referred to as "The Food Basket of the World."

The major metropolitan area of Fresno serves as a hub for transportation, logistics, and processing for the vast quantities of crops grown in the surrounding counties of Tulare, Kings, and Madera. The continued growth in population and business activity in these areas is the direct reason for the need to introduce the new 357 overlay code. The region is a key player in state and national supply chains, making the stability of its telecommunications infrastructure paramount.

The introduction of the 357 overlay is a clear sign of the region's continued expansion. While the shift to 10-digit dialing requires a small adjustment, it ensures that the Central California region has a robust supply of phone numbers to support new businesses, residents, and technologies for years to come.